The class of elastomeric terpolymers of ethylene, propylene and diene monomer, conventionally referred to as EPDM polymers, is well known and has gained substantial commercial acceptance. The terpolymers are known to be useful in the production of extruded or molded articles useful for construction applications and for housings in the automotive and electrical industries. It is also known that the terpolymers can be crosslinked or vulcanized by methods which are conventional in the rubber industry, e.g., treatment with sulfur and an accelerator. In certain applications, however, the elastomeric terpolymers are difficult to process unless compounded by relatively large amounts of other materials. In many instances, the ease of processing will depend upon how "rubbery" the terpolymer is and in general, the more elastomeric the terpolymer is, the more easily it will be processed.
A number of proposals have been made to improve the processability of the ethylene-propylene-diene monomer terpolymers. In Yamamoto et al, U.S. Pat. No. 4,125,699, there are disclosed ethylene-propylene-diene monomer terpolymers having a relatively high ethylene content produced in the presence of a vanadium-containing catalyst. The polymers of Yamamoto et al are said to have improved processability because of a relatively broad molecular weight distribution. Vanadium catalysts are of relatively low activity and many if not most of the more recent commercial ethylene-propylene-diene monomer terpolymers are produced with a titanium-based catalyst because of the higher catalytic activity available through the use of such a catalyst.
In determining the elastomeric character of the ethylene-propylene-diene monomer terpolymers, a probable very important factor is the distribution of the monomeric moieties throughout the terpolymer. Without wishing to be bound by any particular theory, it appears likely that each monomer, ethylene for example, can serve to disrupt the crystallinity of a portion of a polymerized other monomer, e.g., propylene, through the prevention of block polymerization of other monomer. This disruption results in less crystallinity in the terpolymer molecule and increased elastomeric character. If any monomer of the terpolymer, and particularly the ethylene or propylene, polymerized predominantly in blocks, the structure of the resulting terpolymer would be "blocky" and the elastomeric character would be relatively low. Alternatively, a highly random structure would lead to greater elastomeric character and an improvement in properties such as processability.
In published Japanese Patent Application 58217507-A there is disclosed the use of a catalyst complex derived from a titanium trichloride, an organoaluminum compound and a phosphorus compound, the catalyst preparation being conducted in the presence of an ether. The product is said to have random character and good processability. A related polymer produced with the use of a catalyst derived from a titanium tetrahalide and an organoaluminum compound, also in the presence of an ether, is disclosed by Makino et al, U.S. Pat. No. 4,506,061. This polymer is also said to have a high degree of random polymerization. It would be of advantage, however, to provide additional ethylene-propylene-diene monomer terpolymers of improved random polymerization character and improved processability.